(1) Field of the Invention
The present invention relates to a transmission with pulleys whose outer diameters are variable.
(2) Description of the Prior Art
In agricultural machines and vehicles with combustion engines, bicycles and various other kinds of machines, step or continuous (stepless) transmissions which can control the number of revolutions of the output shafts are used.
A continuous transmission proposed in Japanese Patent Laid-Open Application 63-145860 provides a pulley in which the outer diameter varies by slide parts dividing a band wheel in a guide wheel with radially disposed gutters. The slide parts and guide blocks which slide on a rotary shaft are linked by a link rod. Another construction, which moves one of the slide plates included in a V pulley, is proposed in Japanese Utility Model 2-54947.
For a variable outer diameter roller using fluid such as compressed air, for example, Japanese Patent Laid-Open Application 3-20420 and Japanese Patent Laid-Open Application 3-259843 propose a roller in which the outer diameter is varied by supplying fluid, such as, a gas, to a pressure chamber (including a combination of a plurality of pressure chambers) made of tubular elastics and fixed to a rotary axle, and then expanding the tubular elastics.
In Japanese Patent Laid-Open Application 63-145860 using the above-mentioned variable outer diameter pulley, however, a link mechanism and slide parts with divided band wheels are used and the construction is complex because a number of parts are used.
Also, in Japanese Utility Model 2-54947, the transmission mechanism is complex, its capacity is large, it requires a large number of man-hours for assembly, and requires large cost expendatures.